Jefferson,
This is almost certainly related to bad connections (ie solder joints) within the circuit. The fact that it is behaving differently even though nothing external has changed indicates to me that something internal has changed…like some connections are intermittent. Please make sure the paper insulation has not been punctured and nothing is shorting to the back of the pots. I suggest reflowing the solder joints (all of them) to ensure that they are all working properly. If you haven’t soldered many projects yet, make sure your iron is getting hot enough and you are using the proper amount of solder on each joint…it’s easy for joints to be bad if there isn’t enough solder on them.
Good luck!
-Brach